Orbitals each sublevel is broken into orbitals each orbital can hold a maximum of 2 electrons orbital- a 3D region around the nucleus that has a high probability of holding electrons

Number of Orbitals sublevel max # e- # orbitals s 2 1 p 6 3 d 10 5

One s orbital spherical

Three p orbitals dumbbell-shaped

Five d orbitals various shapes

Seven f orbitals various shapes

Energy Number of Types of Level Sublevels Sublevels 1 1 s 2 2 s,p 3 3 s,p,d 4 4 s,p,d,f

Energy Level Sublevels # Orbitals Total Orbitals Total Electrons 1 2 3 4

Energy Level Sublevels # Orbitals Total Orbitals Total Electrons 1 s 2 4 8 p 3 9 18 d 5 16 32 f 7

Electron Configurations the arrangement of electrons in an atom each type of atom has a unique electron configuration electrons tend to assume positions that create the lowest possible energy for atom ground state electron configuration- lowest energy arrangement of electrons

Rules for Arrangements Aufbau Principle- an electron occupies the lowest-energy orbital that can receive it Beginning in the 3rd energy level, the energies of the sublevels in different energy levels begin to overlap

Rules for Arrangements Pauli Exclusion Principle- no more than two electrons can occupy an orbital at a time, and they must have opposite spins.

Rules for Arrangements Hund’s Rule- orbitals of equal energy are each occupied by one electron before any orbital is occupied by a second (fill empty orbitals with 1 before pairing)

Rules for Arrangements all unpaired electrons must have the same spin

Rules for Arrangements

Writing Configurations Orbital Notation: an orbital is written as a line each orbital has a name written below it electrons are drawn as arrows (up and down) Electron Configuration Notation number of electrons in sublevel is added as a superscript

Order for Filling Sublevels

Writing Configurations Start by finding the number of electrons in the atom Identify the sublevel that the last electron added is in by looking at the location in periodic table Draw out lines for each orbital beginning with 1s and ending with the sublevel identified Add arrows individually to the orbitals until all electrons have been drawn

Silicon number of electrons: 14 last electron is in sublevel: 3p 1s 2s 2p 3s 3p Valence Electrons- the electrons in the outermost energy level

Chlorine number of electrons: 17 last electron is in sublevel: 3p 1s 2s 2p 3s 3p

Sodium number of electrons: 11 last electron is in sublevel: 3s 1s2 2s2 2p6 3s1 1s 2s 2p 3s

Calcium number of electrons: 20 last electron is in sublevel: 4s 1s2 2s2 2p6 3s2 3p6 4s2 1s 2s 2p 3s 3p 4s

Bromine number of electrons: 35 last electron is in sublevel: 4p 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 1s 2s 2p 3s 3p 1s 2s 2p 3s 3p 4s 3d 4p 4s 3d 4p

Argon number of electrons: 18 last electron is in sublevel: 3p 1s2 2s2 2p6 3s2 3p6 1s 2s 2p 3s 3p

Noble Gas Notation short hand for larger atoms configuration for the last noble gas is abbreviated by the noble gas’s symbol in brackets